Observations of Dispersion Cancellation of Entangled Photon Pairs

An experimental study of the dispersion cancellation occurring in frequency-entangled photon pairs is presented. The approach uses time-resolved up conversion of the pairs, which has temporal resolution at the fs level, and group-delay dispersion sensitivity of $\approx 20{\mathrm{f}\mathrm{s}}^2$ under experimental conditions. The cancellation is demonstrated with dispersion stronger than $\pm {10}^3{\mathrm{f}\mathrm{s}}^2$ in the signal $(-)$ and idler $(+)$ modes. The observations represent the generation, compression, and characterization of ultrashort biphotons with correlation width as small as 6.8 times the degenerate optical period.